The present invention relates to a method for fastening an accessory to a wall of a plastic fuel tank.
Fuel tanks on board vehicles of various kinds must generally meet sealing and permeability standards in relation to the type of usage for which they are designed and the environmental requirements with which they must comply. Both in Europe and throughout the world we are currently experiencing a considerable tightening of the requirements concerned with limiting the emissions of pollutants into the atmosphere and into the environment in general.
To limit these emissions, care is taken in particular to position the accessories (ventilation lines, valves, baffles, stiffeners, etc.) inside the tank and, to limit the number of openings through its wall, the Applicant has developed a method of initially moulding a parison that includes at least one slot for introducing thereinto (and fixing thereto) accessories during the actual moulding of the tank and thus avoiding drilling openings (see, in particular, Application EP 1 110 697).
The Applicant has also developed a particular method for this fastening (in situ snap-riveting, the subject of Application WO 2006/008308, the content of which is incorporated for this purpose for reference into the present application) and also an improvement of this method taking into account the fact that as the tank cools down after moulding it undergoes considerable shrinkage (typically of around 3%). This improved method is the subject of international Application EP 2007/051326 in the name of the Applicant, the content of which is also incorporated for reference into the present application.
One accessory which has been described in FIG. 1 of this application is a support for a valve which comprises two flexible tabs, moulded as one piece with it, and each provided with an orifice that enables the snap-riveting. The Applicant has, however, observed that with the tab geometry illustrated in this figure (simple curved tongues equipped with an orifice in the fastening zone), it was difficult to load this accessory onto the core (the tongues having a tendency to slide outside the enclaves provided for them on the core) and that, in addition, the mechanical stress exerted at the fastening was not uniformly distributed.